1. Field of the Invention
This invention is in the field of mechanical deflocculation of fibrous suspensions by means of controlled gravity settling coupled with sonic vibrations which operate to break up fiber flocs and permit the uniform deposition of a dry fiber layer on a suitable sheet forming means.
2. Description of the Prior Art
In any dry forming process for paper making, one of the most difficult tasks is that of providing a uniform fiber layer on a moving screen or forming fabric. Much of the difficulty comes from the fact that flocs or lumps of fiber tend to be deposited on the screen and non-uniform fiber distribution results.
We are familiar with a few prior U.S. patents which deal with similar problems but propose considerably different solutions. Pearson U.S. Pat. No. 3,126,584 deals with a machine for converting tows of filaments into a fibrous web and utilizes three sets of blades which act upon a tow successively, the first conditioning the tow for breakage, the succeeding sets of blades breaking the tow into fibers.
Langdon U.S. Pat. No. 3,395,426 deals with a machine for forming random fiber webs wherein the fibers are delivered by an air stream between two endless foraminous belts which travel around suction boxes. The belts are disposed with confronting reaches which converge toward one another in the direction of their travel so that they compact the fibers and form them into a mat as the fibers are pulled in between the belts by suction. The mat is delivered between two opening rolls which rotate in opposite directions and at different speeds. An air stream is used to doff the fibers from the rolls and deliver them onto a foraminous condenser by suction so that they are formed into a random fiber web.
Craig U.S. Pat. No. 3,408,697 describes an apparatus for forming a fiber mat wherein random length fibers are deposited on a continuously moving belt and are propelled by air down an inclined diverging chute and discharged into another air stream which directs the fibers in the opposite direction downwardly in a scattered array on the moving belt. The fibers are held on the belt by means of suction applied from below the porous belt.
Langdon U.S. Pat. No. 3,512,218 is similar to the aforementioned Langdon patent in that it provides a machine in which fibers or tufts of fibers are fed to rotating condensers on which the fibers are laid down by suction and the mats of fibers thus produced are doffed by doffing rolls. The mats are fed over feed plates by means of feed rolls to two rotating lickerins which comb the fibers from the mats. The fibers are doffed from the lickerins by centrifugal force and by an air stream flowing through a balancing chamber disposed centrally between the two condensers. The stream is then split into two parts so that it flows past the two lickerins. The two air streams then deliver the fibers doffed from the lickerins into an endless condenser belt on which the fibers are laid down in random fashion.
Radmussen U.S. Pat. No. 3,581,706 describes an apparatus for uniformly distributing a disintegrated material on a forming surface utilizing a cylindrical housing having a perforated plane surfaced bottom wall, an inlet opening for a stream of air containing suspended fibers, and a stirrer having impellers rotating a short distance above the perforated bottom wall. Any lumps or flocs are eliminated by providing a narrow slit in the side wall of the housing close to the screen, together with an air nozzle. The fibrous lumps which exist on the screen will eventually pass the slit where they are exposed to the influence of the air current from the air nozzle and are blown out of the housing.
Lipscomb et al. U.S. Pat. No. 3,736,211 describes an apparatus for improving dispersal and deposition of continuous filaments on a continuously moving surface utilizing a non-moving two-planar deflector which is positioned near the exit of an aspirator to provide greater openness and greater random laydown of the filaments.
Lipscomb et al. U.S. Pat. No. 3,738,894 describes another apparatus for depositing non-woven filaments utilizing a foraminal splaying device having two opposite surfaces with holes extending to at least one of the surfaces. A compressed gas is discharged through the holes in substantially parallel columns to penetrate a filament bundle which passes between the two opposing surfaces. The two opposing surfaces of the splaying device have continuous surfaces of curvature which surfaces exhibit a converging to diverging pattern as the opposing surfaces extend from the exit of the aspirator. The foraminous splaying device is positioned near the exit of an aspirator so as to spread the filaments in substantially all directions and thereby provide a random laydown of the filaments.
Finally, Helgesson U.S. Pat. No. 3,792,943 describes a machine for distributing dry fibers wherein the fibers are suspended in a rising stream of air which is deflected into a distribution chamber having a bottom formed by a gas permeable screen advanced over a suction box. A second stream of air is added to control the inflow of suspended fibers into the distribution chamber and to cause the fibers to follow a predetermined trajectory through the chamber. The pattern of fiber deposition on the moving screen is thus further controlled by admitting additional air from above through an adjustable opening in the enclosure of the distribution chamber.